How to Identify and Measure Fittings
Pipe size is an industry designation, not the actual size. View information about how to measure threaded and unthreaded pipe and pipe fittings.
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Flow-Control Flange Unions
Measure, throttle, and regulate the flow of liquids and gases in your line by adding an orifice plate to these unions. They consist of two flange halves, plus all of the components needed to connect them together. Tighten the jack bolts to separate the flange halves to inspect or replace the orifice plate.
To throttle flow, mount an orifice plate between the two flanges. The orifice plate restricts the flow in order to regulate it.
To measure flow, build the same assembly, except you’ll also connect a differential pressure gauge or transmitter to both flange halves using the threaded ports. Your gauge or transmitter will measure the difference between the pressure before and after the orifice plate. The pressure difference is proportional to flow rate, so you can use that measurement to calculate your line’s flow rate.
Butt-weld flanges are also known as weld-neck flanges; the flange neck has a beveled end that, when flush to pipe, creates a trough for a strong weld. Slip-on weld flanges have no internal stop; slide a pipe through the flange and weld on both sides.
316/316L stainless steel flanges have excellent corrosion resistance.
Flanges that meet ASME B16.36 adhere to specifications and testing requirements for temperature and pressure ratings, dimensions, materials, and tolerances.
- For Use With: Air, Natural Gas, Oil, Water
- Temperature Range: Not Rated
- Specifications Met: See table
- Pressure Class: 300
- Fittings:
Carbon Steel: Use Schedule 40 steel
316/316L Stainless Steel: Use Schedule 40 stainless steel - Pipe Nipples and Pipe:
Carbon Steel: Use Schedule 40 steel
316/316L Stainless Steel: Use Schedule 40 stainless steel
Bolt Hole | Port | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Pipe Size  | Construction | Flange OD | For Bolt Dia. | Dia. | No. of | Bolt Circle Dia. | Pipe Size | No. of | Includes | Specifications Met | Each | |
Carbon Steel | ||||||||||||
| 1 | Seamless | 4 7/8" | 5/8" | 11/16" | 4 | 3 1/2" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N12 | 0000000 |
| 1 1/2 | Seamless | 6 1/8" | 3/4" | 13/16" | 4 | 4 1/2" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N13 | 000000 |
| 2 | Seamless | 6 1/2" | 5/8" | 11/16" | 8 | 5" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N14 | 000000 |
| 3 | Seamless | 8 1/4" | 3/4" | 13/16" | 8 | 6 9/16" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N15 | 000000 |
| 4 | Seamless | 10" | 3/4" | 13/16" | 8 | 7 7/8" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N16 | 000000 |
316/316L Stainless Steel | ||||||||||||
| 1 | Seamless | 4 7/8" | 5/8" | 11/16" | 4 | 3 1/2" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N25 | 000000 |
| 1 1/2 | Seamless | 6 1/8" | 3/4" | 13/16" | 4 | 4 1/2" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N26 | 000000 |
| 2 | Seamless | 6 1/2" | 5/8" | 11/16" | 8 | 5" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N27 | 000000 |
| 3 | Seamless | 8 1/4" | 3/4" | 13/16" | 8 | 6 9/16" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N28 | 000000 |
| 4 | Seamless | 10" | 3/4" | 13/16" | 8 | 7 7/8" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N29 | 00000000 |
- For Use With: Air, Natural Gas, Oil, Water
- Temperature Range: Not Rated
- Specifications Met: See table
- Pressure Class: 300
- Fittings:
Carbon Steel: Use Schedule 40 steel
316/316L Stainless Steel: Use Schedule 40 stainless steel - Pipe Nipples and Pipe:
Carbon Steel: Use Schedule 40 steel
316/316L Stainless Steel: Use Schedule 40 stainless steel
Bolt Hole | Port | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Pipe Size | Flange OD | For Bolt Dia. | Dia. | No. of | Bolt Circle Dia. | Pipe Size | No. of | Includes | Specifications Met | Each | |
Carbon Steel | |||||||||||
| 1 | 4 7/8" | 5/8" | 11/16" | 4 | 3 1/2" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N18 | 0000000 |
| 1 1/2 | 6 1/8" | 3/4" | 13/16" | 4 | 4 1/2" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N19 | 000000 |
| 2 | 6 1/2" | 5/8" | 11/16" | 8 | 5" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N21 | 000000 |
| 3 | 8 1/4" | 3/4" | 13/16" | 8 | 6 9/16" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N22 | 000000 |
| 4 | 10" | 3/4" | 13/16" | 8 | 7 7/8" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N23 | 000000 |
316/316L Stainless Steel | |||||||||||
| 1 | 4 7/8" | 5/8" | 11/16" | 4 | 3 1/2" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N32 | 000000 |
| 1 1/2 | 6 1/8" | 3/4" | 13/16" | 4 | 4 1/2" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N33 | 000000 |
| 2 | 6 1/2" | 5/8" | 11/16" | 8 | 5" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N34 | 000000 |
| 3 | 8 1/4" | 3/4" | 13/16" | 8 | 6 9/16" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N35 | 00000000 |
| 4 | 10" | 3/4" | 13/16" | 8 | 7 7/8" | 1/2 NPT | 2 | Gaskets, Jack Bolts, Nuts, Port Plugs, Threaded Rods | ASME B16.36 | 5291N36 | 00000000 |